Gene therapy, the correction of genetic defects by site-specific transgene expression in vivo, will revolutionize the treatment of human disease. Molecular defects underlying human lung malignancy, including the over expression of transforming oncogenes or the loss of tumor suppressor genes, have been characterized in detail. However, the inability to achieve high level expression of transgenes in the lung has precluded translation of these molecular analyses into effective gene therapy for lung cancer. We have demonstrated high levels of transgene expression in the lungs of mice for up to 60 days following either aerosolization or intravenous (iv) injection of expression vectors complexed to cationic liposomes into normal animals. We have also efficiently transfected metastatic lung tumors and intravascular tumor emboli after iv injection of cationic liposome-reporter gene complexes into tumor-bearing mice. We have documented high level expression of CFTR, GM-CSF and CAT transgenes in the lung, and have observed no histologic evidence of toxicity in any treated mice. We now propose to further develop our in vivo gene delivery technology, to create effective gene-based therapies for human lung cancer. Our 2 main goals are: 1) To maximize the level, duration and cellular-specificity of GM-CSF and p53 transgene expression we can achieve in the lungs, and specifically within lung tumors of tumor-bearing mice by cationic liposome-mediated aerosol and/or iv gene delivery. To accomplish these goals, we will first determine the parameters which maximize cationic liposome-mediated transfection of cultured cells. Second, we will use this data to maximize transgene expression in rodents by optimizing: A) transgene promoter-enhancer element, B) cationic liposome formulation, C) DNA to liposome ratio, D) gene dosage and E) frequency/duration of administration. We will use immunostaining to identify the specific cell types which are transfected in vivo. 2) To then maximize the anti-tumor effects of the p53 and GM-CSF transgenes in tumor-bearing mice. Specifically, we will test whether A) high level, intrapulmonary expression of the GM-CSF transgene can produce significant anti-tumor effects in mice bearing a lung metastatic subclone of B-16 melanoma, or B) expression of the wildtype p53 transgene in vivo can produce anti-tumor effects against the human lung cancer line NCI- H358, grown in the lungs of nude mice. NCI-H358 carries a homozygous deletion of p53, and this line is growth arrested in culture after lipofection of a wild-type p53 expression plasmid. In summary, we will optimize the level, duration and cellular specificity of cationic liposome-mediated transgene expression we can now achieve in vivo, while minimizing host toxicity. Our overall goal is to develop safe and effective, genetically-based in vivo treatments for lung cancer. The ability to express transgenes in the lung, and specifically within lung tumors is an essential step towards achieving this goal.